This invention relates to an optical glass and, more particularly, to an optical glass of a B.sub.2 O.sub.3 --SiO.sub.2 --SnO.sub.2 --La.sub.2 O.sub.3 --Yb.sub.2 O.sub.3 system which is stable in spectral transmissivity and is scarcely liable to tinting and has optical constants in a high refractive and low dispersive region on the left side of a line a connecting a point where nd is 1.68 and .nu.d is 56.0 and a point where nd is 1.82 and .nu.d is 45.0 in the co-ordinates shown in FIG. 1 of the accompanying drawings.
There is disclosed in Japanese laid-open patent publication 2717/1976 an optical glass which has substantially the same optical constants as the present invention and consists essentially of a B.sub.2 O.sub.3 --La.sub.2 O.sub.3 --Yb.sub.2 O.sub.3 system. This prior art optical glass is not stable in spectral transmissivity due to its melting conditions and besides is liable to tinting. The prior art optical glass therefore is disadvantageous when it is used as high grade lenses suitable for taking colour pictures.